A video mixer is a processing device that receives video streams signals) from multiple different video sources and mixes the video streams to form a composite video stream. Mixing may also be referred to as “compositing.” By way of example, video mixers are used in video conferencing systems. In such systems, the video mixer typically receives individual video streams from conference participants and generates a composite video stream by mixing (compositing, combining) the individual streams into one stream. The composite video stream is then sent back to the conference participants. Note that video mixers also typically mix audio associated with the video streams.
Thus, a video mixer may also be called a “multipoint control unit” (MCU) since the mixer receives the multiple video streams from the multiple conference participants, combines the multiple streams (via mixing/compositing) to produce the single composite stream, and sends the single composite stream back to each of the multiple participants. The composite stream enables each participant to view on one display screen the video images of the other participants, perhaps along with his or her own video images, in real time. The processing device used by each participant to participate in the video conference is typically called an endpoint.
In the video conferencing system scenario, since bandwidth and latency issues can be a problem, existing architectures typically mix video (and audio) at a single point (e.g., at the MCU), and export the mixes to all participants of the conference, as explained above.